A pin-barrel extrusion device generally of the above type is disclosed in German Offenlegungsschrift No. 2,931,387. In the arrangement shown in FIG. 1 of such prior document, there is shown an inner hollow cylinder having an outer hollow cylinder coaxially disposed therearound. The rate of wear of the inner cylinder depends upon the material being processed and hence such cylinder must be made interchangeable.
Helically encircling temperature control passages are disposed in the annular gap between the inner and outer hollow cylinders. Moreover, pins protrude radially inwardly thrugh the cylinders to lie adjacent the core of the extrusion screw which rotates in the inner cylinder or barrel.
Frictional heat is produced during the operation of such a pin-barrel extrusion device, which heat causes thermal expansion of the inner cylinder. Such expansion may be of the order of 1 mm if the operating temperature is 100.degree. C. and the length of the barrel portion is approximately 100 cm.
The thermal expansion of the outer hollow cylinder is less than that of the inner cylinder because it can dissipate heat radially outwardly to ambient atmosphere. Accordingly, relative movement occurs between the inner hollow cylinder and the outer hollow cylinder in the longitudinal direction of the barrel portions. This relative movement produces large stresses on the pin bodies protruding through the cylinders, which stresses may result in the pin bodies becoming deformed or even breaking.